I need some pattern help. With right side facing work on rem 24 sts slip 10 sts on to a stitch holder rejoin yarn to rem 14 sts knit to end . The next row is purl.
Work 4 rows dec 1 st at neck edge in every row (12sts) work 4 rows dec 1 st at neck edge in next in next and foll alt row 10 sts
Work 9 rows dec 1 st at neck edge in next and every foll 4 th row 7 sts

I need some pattern help. With right side facing work on rem 24 sts slip 10 sts on to a stitch holder rejoin yarn to rem 14 sts knit to end . The next row is purl.
Work 4 rows dec 1 st at neck edge in every row (12sts) work 4 rows dec 1 st at neck edge in next in next and foll alt row 10 sts
Work 9 rows dec 1 st at neck edge in next and every foll 4 th row 7 sts

Where do I use the stitches on stitch holder?

Having not read the full pattern, and not knowing a) if it's for a child or an adult and, b) if it's a cardi or pullover, or c) where you are in the pattern on it's kind of hard to say.

If I had to guess, I'd say those 10 sts on the holder could be either an armhole/part of an armhole or part of the neckline, depending on some of the things above.

Do you have a picture or pattern you can link to? That will really help out when the experts chime in.

Sounds like part of the neck on a sweater front. Check under the collar or neckband instructions near the end of the pattern or under Finishing.

It may be a mistake in copying but the stitches don't add up for the decreases as written: "With right side facing work on rem 24 sts slip 10 sts on to a stitch holder rejoin yarn to rem 14 sts knit to end . The next row is purl. Work 4 rows dec 1 st at neck edge in every row (12sts)"
If you have 14sts and dec one st in every row over the next 4 rows, you should end with 10sts not 12. Maybe it's dec at neck edge on the RS rows only (that is, every other row)?